Bleaching stages of rhodopsin (and possibly iodiosin) will be investigated under physiological conditions. These stages have been studied at low temperatures, where they are stable and can be isolated, but their spectral and kinetic properties have not yet been determined under physiological conditions. It is not even definitely known whether all the known stages exist under physiological conditions or whether additional stages appear. This study will use techniques of kinetic spectroscopy with an apparatus capable of nanosecond time resolution to investigate the bleaching stages. The goals of research are: 1. To determine what bleaching stages exist under physiological conditions. 2. To determine the spectra of the stages under these conditions. 3. To determine the kinetic behavior of the bleaching stages unde these conditions. 4. To determine when conformational changes occur in rhodopsin by studying the polarization spectra of the bleaching stages.